The present invention relates, in general, to microelectromechanical motion (MEM) amplifiers, and more particularly to microelectromechanical structures wherein a small driving motion in an axial direction applied to a structure produces a relatively large motion in a direction transverse to the axial drive motion, thereby amplifying the drive motion, the structure of the invention providing an amplification of about two orders of magnitude.
In micromechanical systems, for example of the type illustrated in U.S. Pat. No. 5,506,175 to Zhang and MacDonald, motion of a rigid MEM body is typically obtained by attaching that body to an actuator which is then activated to generate the motion.
The actuator may include a fixed portion and a relatively movable portion supported by a set of springs formed from released structural beams, with motion of the movable part of the actuator deforming the springs. The force required to deform the springs and thus move the actuator may be obtained, for example, by the use of parallel plate or comb capacitors actuators, by differential heating of actuators, or by other controllable force generators.
In spring-supported devices, the resisting force of the supporting springs varies linearly with deformation as long as the deformation is small; however, for larger deformations, the force required to move the spring varies nonlinearly, primarily as the cube of the deformation, with the nonlinear terms of the spring restoring force becoming dominant. Thus, the applied force generated by the actuator has to be increased nonlinearly for large increments of deformation, and this requires prohibitively large voltages for electrical actuators such as capacitors. Furthermore, if the actuator is a parallel plate capacitor, the available motion is limited by the gap between the parallel plates, while if the actuator is a comb capacitor, large motion involves a large overlap between the combs which, together with the high voltage required, may produce an unstable actuation. These factors have limited the maximum available controlled deformation of such micromechanical devices to only several micrometers.